The proposed research will use selective lesion techniques to assess the role of the hippocampal formation, perirhinal cortex and parahippocampal gyrus (TH/TF) in recognition memory in rhesus monkeys. Specifically, ibotenic acid lesions of the hippocampal formation will be compared to aspiration lesions of the perirhinal cortex and parahippocampal gyrus (TH/TF) on newly designed behavioral tasks. The visual recognition tasks, delayed nonmatching-to-sample and preferential looking will be used to test the effects of these lesions on spatial recognition memory and on contextual recognition memory. For spatial recognition, in both tasks, the monkeys will be required to respond (touch or look at, respectively) a new location on the screen. For contextual recognition, in both tasks, the monkeys will be required to respond to the new object when the context in which the object is learned has been changed. Results from these experiments will permit elucidation of the respective contributions of the hippocampal formation, perirhinal cortex and parahippocampal gyrus (TH/TF) in spatial and contextual recognition memory.